1. Field of the Invention
The present invention generally relates to optical amplifiers, and more specifically, to a Fourier plane image amplifier.
2. Description of Related Art
The ablation of polymers at short wavelengths is a technique being used to construct the interconnect boards in the production of multichip modules (MCMs). Thousands of holes of approximately 10 .mu.m to 25 .mu.m diameter need to be drilled in the insulating layers of multi-layer boards in order to generate the interconnect pathways. In "Eximer Laser Ablation of Polyimide in a Manufacturing Facility," Applied Physics A54, 1992, Lankard and Woldbod of IBM have discussed a laser based system which illuminates an appropriately patterned mask with a high power beam and then relays this illuminated image onto the circuit board. This tool has been shown to be effective for the rapid ablation of a polyimide insulating layer in this application. Their process employs an eximer laser of relatively high peak power (.about.10 MW at 308 nm) for ablation and a relatively high average power (150 W) because the transmission through the holes of the mask is only about 1%. A laser of this power level is relatively expensive (.about.$300,000) and the high power loading requires expensive masks. Since this process only uses .about.1% of the generated laser energy, there is significant room to develop a more efficient and lower cost design.